Research On Orbit Determination And Ephemeris Fitting Of LEO Satellites Based On Spaceborne Receiver

In order to improve the positioning accuracy of the navigation system,the low orbit satellites’ orbital height and strong signal characteristics can be used to broadcast navigation information and navigation signals.This paper aiming at the low-orbit satellite navigation enhancement technology,this paper studies the differential phase between epochs to calculate the position difference between epochs,constructs a high-precision motion model,and realizes the method of determining the orbit of the low-orbit satellite through Kalman filtering-the difference between the epochs and the double Orbit determination method for combined observations of the high-precision difference phase.This method is also applicable to singlepoint positioning.The fitting of broadcast ephemeris parameters suitable for low-orbit satellites is further studied.The use of low-orbit satellites to broadcast ephemeris can be combined with the navigation system to enhance the geometric configuration between the ground station and the satellite,so that ground users can also obtain reliable and continuous position information provided by the navigation system in a complex environment.positioning accuracy.The main work and results are as follows:1.The GPS data of 1s sampling rate from Hong Kong Geodetic Observation Station is used to verify the applicability of this method to single-point positioning.After experimental verification and analysis,it is concluded that the filtering convergence time of this method is about 21 minutes,and the positioning result accuracy of this method is Expressed in the E,N and U directions,the positioning accuracy(RMS)in each direction reached 0.61 m,0.21 m and0.52 m,and the three-dimensional accuracy reached 0.83 m.Compared with the traditional dualfrequency single-point positioning method,the positioning accuracy is improved by 29.07%,72.37% and 77.68% in all directions.This method uses dual-frequency combined observations.The positioning results show that the positioning results using carrier waves are significantly improved over pseudo-ranges,and the improvements in the E,N,and U directions are 14.08%,66.13% and 70.11%.2.Use the actual measurement data of the "Tianhui-1" satellite to verify the applicability of this method to low-orbit satellite orbit determination.After experimental verification and analysis,it is concluded that the filter convergence time of this method is about 20 minutes,and the accuracy of the orbit determination results of this method is expressed in the R,T and N directions,and the orbit determination accuracy(RMS)in each direction can reach 0.62 m,0.74 m and 0.84 m,the three-dimensional precision direction accuracy reaches 1.32 m.Compared with the dual-frequency pseudo-range single-point positioning orbit statutory results,they have increased by 75.0%,73.1%,77.7% and 75.8% respectively;compared with the combination of dual-frequency carrier phase difference between epochs and dual-frequency pseudo-range ionospheric observations.Compared with the orbit method,the improvements in each direction are 39.80%,26.73%,54.35% and 45.30%.Statistics on the convergence time of the expected accuracy sequence of 315 to 318 days per year,this method converges more quickly than the experiment than changing the weight of the position difference.3.The satellite transmits the orbit information to the ground users by broadcasting the broadcast ephemeris.With reference to the GPS16 parameter broadcast ephemeris combined with the analysis of the period of the orbit element,the broadcast ephemeris with 10 parameters,16 parameters and 22 parameters are studied.The fitting results show that the accuracy of the22-parameter fitting results is significantly improved compared to the 10-parameter and 16-parameter fitting results.22-parameter 15 min fitting time URE is better than 3cm,10 min fitting time URE is better than 0.5cm.The broadcast ephemeris broadcast interval of high-orbit satellites with reference to GPS16 parameters is 2 hours,and its operating cycle is 12 hours.The operating period of "Tianhui-1" low-orbit satellite is 96 minutes,and the user’s fitting accuracy needs to be guaranteed.It is recommended that the fitting duration be 15 minutes.